title: 14-3-3 proteins act as negative regulators of the mitotic inducer Cdc25 in Xenopus egg extracts.
abstract: Cdc25, the dual-specificity phosphatase that dephosphorylates the Cdc2-cyclin B complex at mitosis, is highly regulated during the cell cycle. In Xenopus egg extracts, Cdc25 is associated with two isoforms of the 14-3-3 protein. Cdc25 is complexed primarily with 14-3-3epsilon and to a lesser extent with 14-3-3zeta. The association of these 14-3-3 proteins with Cdc25 varies dramatically during the cell cycle: binding is high during interphase but virtually absent at mitosis. Interaction with 14-3-3 is mediated by phosphorylation of Xenopus Cdc25 at Ser-287, which resides in a consensus 14-3-3 binding site. Recombinant Cdc25 with a point mutation at this residue (Cdc25-S287A) is incapable of binding to 14-3-3. Addition of the Cdc25-S287A mutant to Xenopus egg extracts accelerates mitosis and overrides checkpoint-mediated arrests of mitotic entry due to the presence of unreplicated and damaged DNA. These findings indicate that 14-3-3 proteins act as negative regulators of Cdc25 in controlling the G2-M transition.
authors.affiliation: Division of Biology, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kumagai
authors.forename: P S
authors.initials: PS
authors.lastname: Yakowec
authors.forename: W G
authors.initials: WG
authors.lastname: Dunphy
mesh_terms: D048948:14-3-3 Proteins; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002457:Cell Extracts; D003001:Cloning, Molecular; D004249:DNA Damage; D007399:Interphase / Q000502:physiology*; D008938:Mitosis; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010063:Ovum; D010449:Peptide Mapping; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase; D014981:Xenopus; D020687:cdc25 Phosphatases
chemical_list: D048948:14-3-3 Proteins; D018797:Cell Cycle Proteins; D002457:Cell Extracts; D011506:Proteins; D011993:Recombinant Fusion Proteins; D012694:Serine; D014446:Tyrosine 3-Monooxygenase; D010749:Phosphoprotein Phosphatases; D020687:cdc25 Phosphatases